The present invention relates to the field of so-called liquid-ring pumps having a vane wheel, arranged eccentrically within a housing, which revolves while engaged with a ring of rotating liquid.
Electric machines known in the art as liquid-ring pumps generally are employed as pumps for a gaseous medium. A housing for such a pump surrounds a ring of rotating liquid which is caused to rotate by an eccentrically mounted vane wheel turned by a revolving shaft. The shaft, in turn, is supported at each end in an end bell having inlet and outlet ports for the gaseous medium to be pumped as well as at least one inlet for operating liquid which replenishes any liquid lost, for example, through evaporation into the pumped medium. Because of the eccentric mounting of the vane wheel, operating liquid on one side of the vane wheel creates a suction zone in which zone the pumped gaseous medium is sucked into the pump by way of the inlet ports in the end bells. On the other side of the eccentrically mounted vane wheel, a pressure zone is created where the pumped gaseous medium is forced to exit the pump by way of the outlet ports in the end bells. Between the end bells and the vane wheel housing or comprising a part of the end bell itself is a control disc which partitions the end bell into separate chambers for operating liquid and pumped gaseous medium as well as provides control openings for the entry and exit of both operating liquid and gaseous medium. The control disc is typically sealed with the end bell on one side and seals the housing on the other side. At the same time, the control disc is designed to comprise separate pressure and suction slots for the pumped gaseous medium concentrically arranged outside a hub of the vane wheel. Also, an opening for operating liquid is typically arranged in the vicinity of the vane wheel hub so that the operating liquid further fulfills the function of a gap sealing liquid sealing the gap between the vane wheel hub and the control disc.
One such liquid-ring pump is known from German Auslegeschrift No. 1027358, in which a first part of operating liquid for the machine accordingly warmed up by the action of the rotating vane wheel is taken from the rotating liquid ring via an opening in a control disk behind the end of a pressure slot of the disc. The liquid is then fed via a radial transfer slot to a ring slot concentric with the shaft which is covered by a hub of the vane wheel and from which ring slot the warmed liquid part flows radially via the entire circumference of the ring slot as a gap-sealing liquid toward the rotating liquid ring. A second, colder partial quantity of the operating liquid replaces the liquid-ring losses and is fed from the outside at lower pressure via an opening not covered by the vane wheel hub between the end of the suction slot and the beginning of a pressure slot to the liquid ring. A liquid separator may be used following the outlet of the control disk to condense evaporated liquid lost from the liquid ring machine which is cooled and returned to the machine for recycling.
In other known liquid-ring pump designs (for example, one disclosed in U.S. Pat. No. 4,545,730), the colder partial quantity of operating liquid is fed-in from the outside, for example, from a source under pressure and mixed in an end bell of the pump with the partial warmer quantity accumulating in the sump of the end bell from the liquid ring. The colder partial quantity is returned mixed with the warmer quantity via a suitable passage in the control disk to the rotating liquid ring in the housing, said passage being located in the region between the end of the suction slot and the beginning of the pressure slot.
In these known cases, the amount of operating liquid fed to the rotating liquid ring, at least in the vicinity of the suction slot, is warmer than the cold portion of liquid entering the machine which makes the desirable condensation effect worse in this region in the case of high humidity or water-vapor suction. Undesirable evaporation of the liquid in the pump is increased if dry gas is transported through the machines.
Consequently, it is highly desirable to improve, in such liquid-ring pumps the condensation effect in the vicinity of the suction slot and to reduce the evaporation effect if dry gas is transported thereby increasing the overall suction capacity of the pump.